diff --git a/remoting/src/main/java/org/apache/rocketmq/remoting/netty/NettyRemotingServer.java b/remoting/src/main/java/org/apache/rocketmq/remoting/netty/NettyRemotingServer.java
index be02d0f9a97..578c102daa4 100644
--- a/remoting/src/main/java/org/apache/rocketmq/remoting/netty/NettyRemotingServer.java
+++ b/remoting/src/main/java/org/apache/rocketmq/remoting/netty/NettyRemotingServer.java
@@ -525,6 +525,7 @@ protected void channelRead0(ChannelHandlerContext ctx, ByteBuf msg) {
             } else if (tlsMode == TlsMode.ENFORCING) {
                 ctx.close();
                 log.warn("Clients intend to establish an insecure connection while this server is running in SSL enforcing mode");
+                throw new UnsupportedOperationException("The NettyRemotingServer in SSL enforcing mode doesn't support plain client");
             }
 
             try {